In the Maths of Life, Prof. Sophie Scott looks into why we can’t tickle ourselves, and why we laugh in the first place. On This Week’s Watchlist, Rhianna Dhillon reviews new Beyoncé documentary Homecoming, BBC One’s dark comedy Back to Life, and a taster of Avengers: Endgame. Stephen Graham joins us to talk about his new show The Virtues, written and directed by Shane Meadows. He also chats about working with his heroes, and his role in the latest series of Line of Duty.